On Mon, Jan 05, 2004 at 09:56:00PM -0500, Gregory (Grisha) Trubetskoy wrote: > > Hi - > > I've been using FreeBSD jail for a while, but am new to Vserver, which > seems like cool stuff, I'm thinking of using it for hosting customers. > I've got a few questions for the list. > > 1. On FreeBSD, a common way to share files across virtual servers is to > mount them using unionfs read-only, which allows basically one part of a > file-system to be mounted in another place. > > The idea is to then symlink all important files shared across jails to > that mount point to save space. The user of the virtual server can then > delete the symlinks as he wishes to replace them with real files (which > will take up more space). > > First, there doesn't seem to be anything like unionfs on Linux (mount > --bind doesn't really allow read-only mounting). I'm thinking NFS might do > the trick, though.
there is a patch, I did some time ago, and tried to get into Marcello/Andrew kernel, but it wasn't accepted yet, which allows ro --bind mounts ... http://vserver.13thfloor.at/Experimental/patch-2.4.22-rc2-bme0.03.diff http://vserver.13thfloor.at/Experimental/patch-2.6.0-test3-bme0.03.diff and there is the concept of immutable but unlinkable shared files (called unification) which might be more powerful than a unionfs in some cases ... > Has anyone tried a set up like this, or are people generally happy with > using the hard links as described in the vserver docs? It seems to me > there is an advantage to symlinks in that you can modify the files that > the links point to and the change is immediate across all virtual servers. > Plus, symlinks make it a bit more apparent to the user on what's going on > (although sometimes you may not want this) and make space accounting > simpler. that is not exactly the idea behind that, but you'll see if you give it a try ... > 2. Another thing common in the BSD world is to place jails into vnode file > systems - i.e. a filesystem mounted from an image file, same as the mount > loopback on Linux. This is a pretty efficient way to restrict disk space, > but, of course you won't be able to use hard links in this set up since > hard links cannot cross filesystems. > > The only other alternative to restricting space seems to be the context > quota patch - does this work reliably? What does df show from within the > vserver? yes, if done properly, this does work reliably, and it shows you exactly what you want to see there ;) > Basically I'm a bit torn between trying to set up virtual servers using > the ways I learned in FreeBSD - loopback filesystem, nfs mounted read-only > directory with symlinks, or giving up on that idea and just doing using > the context quota and the hard links as described in the vserver faqs. > > Has anyone gone through this experience? yup, just visit the irc channel an have a talk with some folks there ... HTH, Herbert > Thanks, > > Grisha > _______________________________________________ > Vserver mailing list > [EMAIL PROTECTED] > http://list.linux-vserver.org/mailman/listinfo/vserver _______________________________________________ Vserver mailing list [EMAIL PROTECTED] http://list.linux-vserver.org/mailman/listinfo/vserver
